When i run the PHP requirement tests i get the following results at the top:

Warning: session_start() [function.session-start]: open(/var/php_sessions/sess_d527f25d4cfbf1fcffd332a9d7540fa4, O_RDWR) failed: No such file or directory (2) in /hermes/bosweb/web073/b734/ipg.beatingtheindexcom/wordpress/wp-content/plugins/si-captcha-for-wordpress/captcha-secureimage/test/index.php on line 18

The PHP session directory is not readable on your server. Your web host
needs to fix that. Make a trouble ticket. show them the test page with error.
The problem is:
No such file or directory: /var/php_sessions